Since the oscillation wavelength of a laser diode used for an optical communication module or the like is influenced significantly by a temperature, the temperature of the laser diode needs to be controlled. In order to control the temperature of the laser diode, a Peltier module for laser diode is used.
For example, Japanese Patent Laying-Open No. 2003-197982 (PTD) discloses a Peltier device thermoelectric conversion module used for adjusting the temperature of a laser diode. In the Peltier device thermoelectric conversion module disclosed in this document, a thermoelectric semiconductor element and a land portion of a ceramic substrate are joined to each other with gold-tin eutectic composition solder.